Did El Niño fuel Arizona's summer heat?

Meteorological summer (recorded from June to August) was laden with heat waves on every continent, and paired with a burgeoning El Niño on track to become the strongest ever recorded, pumping warm, moist water vapor into the atmosphere. 

An important distinction is the use of “warmest” as opposed to “hottest,” as some are saying online. While there were some scorching highs recorded, it’s the lack of heat relief overnight that’s led to such high average temperatures, especially across the Northern Hemisphere. It’s something Arizonans know well. 

In Phoenix, 27 nights had lows at or warmer than 90 degrees, 14 of which broke or tied daily records.

No overnight lows reached 90 degrees in Tucson between June and September. However, Tucson did have 27 nights at or above 80 and two nights at or above 85 this summer, weather records show.

Warmer lows shorten the range of the overall average temperature, which combines daily highs and lows. This summer’s average temperature was 97 degrees, tying it for Phoenix’s second-warmest ever with summer 2023, only beaten by summer 2024. 

Though record-breaking high temperatures were not as widely recognized in Phoenix, there were definitely some lengthy heat streaks: 39 days were above 110 and nine of those were above 115. That puts summer 2026 at the fourth-highest quantity of each benchmark, behind years like 2024, 2023 and 2020.

Among the warmth records in the United States, the Southwest region was the primary driver — each of the Four Corners states saw its warmest summer, with multiple counties beating records. This includes most of Utah, the eastern two-thirds of Colorado and New Mexico, plus eastern and southeastern Arizona. 

Regarding rainfall, Arizona as a whole isn’t doing too bad. Most of the state is still below average on precipitation for the whole year, but monsoon rainfall has performed near average overall. Phoenix is only 0.45 of an inch below normal, Flagstaff is 0.62 of an inch below normal, and Tucson is 0.54 of an inch above normal. Parts of the western Mogollon Rim, northern Arizona and southeastern Arizona all received above-average rainfall. There are still a few weeks in the monsoon season before the final tallies are taken.

Has El Niño played a part in Arizona's summer?

Generally, the summer in Arizona is characterized by extremely hot temperatures and monsoon storms. The hot temperatures are not usually associated with El Niño, and there’s no conclusive data that points to increased rainfall, either. Research at the beginning of the monsoon by the National Weather Service in Phoenix showed that El Niño-influenced monsoons tend to have near- or above-normal rainfall, but there is no overwhelming correlation.

Forecasters compared years where El Niño was emerging, ongoing and ending, and the rainfall totals during each season. Overall, 38.5% of events were above normal, 42.3% were near normal, and 19.2% were below normal. 

Specifically, during emerging El Niño years, there are equal chances of above- or near- normal rainfall. This year, 2026, is an emerging El Niño year, and rainfall has fallen near normal when averaged across the whole state.  

During the summer, El Niño is usually building strength for when its impacts are most widely seen — during the winter. Upward-rising water vapor from a warming Pacific Ocean is known to lead to atmospheric warming across the globe given the sheer size of the sea. Its most pronounced impact on the summer is on hurricane seasons; this year has been an aggressive example.

Increased wind shear in the Atlantic Ocean has stifled the season to a historic point: There have only been five named storms, none of which have become hurricanes. This means the first one that does finally form will be the latest first hurricane in the satellite era when it appears. Meanwhile, record-warm ocean waters and lowered wind shear has amplified the Pacific hurricane season: 16 storms have been recorded, four of which became major hurricanes (Category 3 or greater). 

Monsoon season moisture can possibly originate from Pacific hurricanes. September tropical systems are more capable of curving northward, and some of their moisture can move into the Southwest region. The recent Hurricane Marie is a prime example. In the early weeks of September, moisture pulled into the Southwest, leading to showers and storms in New Mexico, Arizona and California. It also brought tropical humidity levels along the southern California coast, making it feel more like South Florida or the Gulf Coast, while high surf stripped beaches bare, leaving little to no sand behind and flooding streets along coastal parts of town. 

The highly conducive environment El Niño provides can lead to a higher number of Pacific storms, which indirectly creates a higher likelihood of some of the storms affecting the Southwest. 

Looking toward the fall, forecasts already point to an increased possibility of above-average precipitation and temperatures in Arizona. How this plays out, including how the monsoon season closes, is worth watching.